The Science of Yoga by William J. Broad – a review

Hey, remember that book that caused all that ruckus in the yoga world a few months ago?  You know, before that other thing happened in the yoga world and caused that other big ruckus?  Well, I just read it.  And despite a few good chapters, most of it is pretty mediocre, with a few interesting forays into the bloody awful.  In more depth:

The good:

  • The first three chapters are very interesting, and review both the modern history of yoga and research into the physiological effects of yoga.  For example, yoga is not an aerobic activity, despite popular beliefs to the contrary.  Yoga does not accelerate metabolism, it slows it down.  Also, yoga most certainly does not increase oxygenation of the blood, which is more or less constant in healthy individuals.  On the contrary, pranayam’s physiological effects are due to the changes it makes to blood levels of carbon dioxide.  Rapid breathing (kapala bhati, bhastrika) decrease blood levels of CO2, contracting arteries, and decreasing the absorption of O2 by the body and the brain.  Slow breathing (ujjayi) increases blood levels of CO2 (or rather, slows its rate of removal), thus dilating arteries and increasing the absorption of O2 by the body and brain.  This explains the exhilarating effects of kapala bhati and bhastrika, and the calming effects of ujjayi.
  • Yoga shows great promise as an effective treatment for depression and anxiety by drastically increasing levels of the neurotransmitter GABA (gamma aminobutyric acid) in the brain.
  • The nicest thing I can say about the chapter on injuries is that the writing underscores the importance of paying attention to what you’re doing when you practice.
  • In the chapter on healing, Broad makes the case that the lack of any sort of regulation or meaningful certification or licensing of yoga teachers and therapists is dangerous.  This is a good point, and definitely deserves further consideration by the yoga community.
  • The research on women inducing orgasms without any physical stimulation whatsoever is fascinating, but seems tangential.  Yes, these women are yoginis, but this is not a traditional yoga practice.  Nonetheless, it raises interesting questions.  Maybe this reflects an evolution of yoga?  Is this a capacity that only exists in women?
  • Page 218:  “If I have been hard on yoga commercialization [actually, he scarcely mentioned yoga commercialization, but I’ll let this slide], it is because the trend raises fundamental questions that seldom get addressed.  Today, as always, yoga has no social mechanism that sifts through the numerous claims to ascertain the truth, and the commercial blitz with its dynamic goals and competitive agenda seems to make that weakness all the more glaring.  Imagine if Big Pharma had no Food and Drug Administration and other regulatory agencies looking over its shoulder.  The marketing of fake diseases and bogus cures – already a multibillion-dollar embarrassment despite all the bureaucratic scrutiny – would be much worse.”  I am inclined to agree.  There are a lot of charlatans in the yoga world, and a great deal of misrepresentation and outright lying that never gets challenged.

The bad:

  • Broad reports that salamba sarvangasana creates a distinct danger of stroke, due to the flexion of the cervical vertebrae.  Apparently, this risk was first identified over 30 years ago.  If this threat is so pronounced, and was identified decades ago, why does Broad not report on any instances of it happening?  His explanation is that sometimes a blood clot is thrown hours or days after the precipitating event, thus obscuring the cause, but surely if sarvangasana produces such a dire risk, there would be some evidence of this actually occurring.  Right?  So I find the threat of stroke overblown.
  • Most of the yoga injuries that Broad reports are the result of, for lack of a better phrase, practitioner stupidity.  If you fall asleep in paschimottonasana or sit in vajrasana for hours, the culpability for injury is your own, not yoga’s.  Where the injuries Broad reported were not due to practitioner stupidity, they were due to poor instruction or poor alignment/technique.  You should not be putting weight on your head in urdhva dhanurasana.  The cervical vertebrae should certainly not be pushing into the floor in salamba sarvangasana, the upper arms and shoulder blades should be carrying the weight.  And in sirsasana, the arms should be carrying the bulk of the weight, not the top of the head.  To quote one practitioner Broad interviewed (page 124), “I was doing it wrong, and I was pushing myself too hard.”  This seems to be the explanation of most, if not all, of the yoga injuries Broad describes.
  • A handful of case studies of injuries sustained during yoga practice do not amount to a systematic problem with yoga; they amount to sensationalism.
  • Yoga has exploded in popularity over the past ten years, yet most of the peer reviewed (ie, actual scientific) evidence of risk that Broad cites is decades old.  Where are the recent peer reviewed papers on risk?
  • Broad makes a big deal about the increase of US emergency room admissions related to yoga from 2000 to 2002.  From 13 in 2000, to 20 in 2001, to 46 in 2002.  These numbers are miniscule.  While statistically significant, this increase is scarcely worth reporting.  (Also, I resent that I had to run the numbers myself in order to determine their statistical significance; Broad is a science reporter.  He should have known to calculate and report the chi-squared value himself.)
  • Most of the risk/injuries chapter is anecdotal.  If there is a systemic problem with yoga instruction in terms of physical risk, Broad has done an incredibly poor job of reporting it.
  • Sex!  Sex, sex, sex, sex, sex!  Wow.  Broad is obsessed.  Unfortunately, he gets a lot of it wrong.  “Tantra” is not Sanskrit for “yoga sex cult.”  Tantra is much more complex than that, and even so, does not represent all of yoga.  Not by a long shot.  Broad’s reading of yoga as a sexual practice says far more about him, or perhaps, more generously, about Western taboos, than it does about yoga.  Yes, yoga texts sometimes refer to the genitals, to stoking inner fire, to “pleasures, enjoyments, and ultimate bliss.”  But interpreting this solely in sexual terms is awfully reductionist.  Maybe this reflects my own bias, but I think that the parallels that Broad draws between yoga practice and sex research or heavy breathing are a bit forced.  Likewise, his reading of sex into the ancient yogic texts (Hatha Yoga Pradipika, Gheranda Samhita).
  • The scientific studies he cites often lack control groups and have few subjects.
  • In the chapter on creativity, Broad is again forcing the comparisons between yoga and sex.  His argument is essentially “Yoga lights up part of the right brain, and sex lights up similar portions of the right brain, therefore yoga must be sexual.”  Well… maybe.  But not necessarily.  On page 207, he states that “Yoga’s ability to promote a rightward shift [in neural activation] would seem to reinforce the idea that the discipline can act as a sexual tonic.”  Really, I think this is just evidence that Broad sees sex wherever he looks.
  • Suggesting that kundalini practices bear a physiological resemblance to being struck by lightning, and therefore can be expected to produce similar results in terms of creativity to what one lightning victim experienced, is ludicrous (see page 208).  Kundalini may well increase one’s creativity, but the suggested similarity to a lightning strike is completely forced and unnecessary.
  • Broad suggests that maybe in the future, yoga will be seen as a cure for “creative paralysis.  Creative blocks might go extinct…. Maybe world leaders would take up yoga as an aid to their deliberations.”  This strikes me as distinctly utopian.  I hope the reader will forgive my cynicism, but I think yoga – fundamental yoga, a method of calming one’s mental fluctuations – will always be a fringe activity, because it takes work, and we humans are lazy.

The ugly:

  • The book unfortunately suffers from the usual pop-science failing of over simplification of the studies it presents, and unsupported conclusions and idle speculation on the part of the author.  I’ll not mince words; in many places, the journalism was shoddy.
  • This may seem picayune, but I found the way he did the end notes terrible.  It was difficult to determine which citations referred to which portions of the text.  Also, not all of his statements reference the appropriate research, causing me to doubt much of what he claimed.
  • The writing is mediocre; pretty much what you’d expect from a pop-science book (not my favourite genre).  He relied heavily on the formulation “X is by definition Y,” which smacks of laziness, and in some cases was confusing or misleading.

Still with me?  Good!  Here’s my summary:  The first three chapters were pretty good, but the rest of the book is not really worth your time.  Don’t be stupid when you’re practicing (or teaching), and you probably won’t hurt yourself (or your students).


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